This application claims priority of japanese Patent Application No. 2001-146818, filed on May 16, 2001.
1. Field of the Invention
The present invention relate""s to traveling control of a vehicle and, in particular, to an adaptive cruise control (ACC) method and apparatus for selecting a target (i.e., a leading vehicle), by using a laser or radar (called xe2x80x9cforward monitoring devicexe2x80x9d hereinafter), to be followed actively by the vehicle and allowing the vehicle to follow the leading vehicle.
2. Description of the Related Art
The ACC system of a vehicle selects a leading vehicle based on the curve radius of the lane on which a vehicle equipped with the ACC system is traveling, obtained through a steering sensor, etc., and the information about a leading vehicle detected with a forward monitoring device, and allows the ACC equipped vehicle to follow the leading vehicle.
FIG. 1 is a schematic configuration of an ACC system mounted on a vehicle 10.
In FIG. 1, the forward monitoring device 11 detects a leading vehicle with a frequency modulated continuous wave (FM-CW) radar, etc. to monitor the distance between the vehicle 10 and the leading vehicle, and the moving direction of the leading vehicle. The steering sensor 12 detects the operation of the steering wheel operated by the vehicle operator, and the vehicle speed sensor 14 detects the traveling speed of the vehicle 10.
The ACC system 13 determines the curve radius, etc. comprehensively based on the information from the forward monitoring device 11, the steering sensor 12, and the vehicle speed sensor 14, and gives a suitable instruction for allowing the vehicle to follow the leading vehicle to the forward monitoring device 11 and the drive control unit 15 for driving the engine, brake, etc. A yaw rate sensor to detect the speed of the vehicle turning a curve may be used instead of the steering sensor 12.
By the way, as a conventional ACC system 13 computes the curve radius in such a manner that the information about the operation of the steering wheel is directly reflected by the curve radius, it has the problems as shown in FIG. 2 and FIG. 3 when the ACC equipped vehicle follows a leading vehicle.
FIG. 2 shows that the curve radius of the lane on which an ACC equipped vehicle is traveling is misjudged due to a strong side wind.
In this case, the vehicle 20 is approaching the ACC equipped vehicle 10 traveling forward on a straight lane (shown with solid lines), and a strong side wind is blowing from the left side to the right side of the vehicle 10. In this state, the-operator of the vehicle 10 turns the steering wheel slightly to the left against the side wind to maintain straight-ahead driving.
The turning of the steering wheel to the left is reflected by the curve radius computed on demand by the ACC system 13, and thus the ACC system makes an erroneous judgment that the vehicle 10 is traveling on a lane (shown with dotted lines) curved to the left. As a result, the range to be monitored by the forward monitoring device 11 concentrates on the lane curved to the left due to the instruction from the ACC system 13, and cannot be corrected by the curve radius.
FIG. 3 shows that the curve radius of the lane on which an ACC equipped vehicle is traveling is misjudged due to the slope of the road surface provided for improving the drainage of the road.
In this state, the operator of the vehicle 10 drives the vehicle while turning the steering wheel slightly to the left against the slope of road surface. As a result, the range to be monitored by the forward monitoring device 11 concentrates on the lane curved to the left due to the instruction from the ACC system 13, and cannot be corrected by the curve radius.
It is therefore an object of the present invention to provide a method and apparatus, in an ACC system for a vehicle, for correcting the curve radius of the lane on which the vehicle is traveling, which improves the accuracy of the selection of a leading vehicle by correcting an actual curve radius on demand by comparing the inputted actual curve radius with the curve radius assumed by monitoring the movement of the leading vehicle detected by the forward monitoring device.
In one aspect, the present invention provides a method for correcting the curve radius of the lane on which the vehicle is traveling, comprising: detecting the curve radius by a curve detection sensor; determining whether a curve radius is wrong based on the first detected position and the present position of a leading vehicle; computing a virtual curve radius based on the detected information about the leading vehicle; and synthesizing the horizontal relative position for the curve radius and the horizontal relative position for the virtual curve radius.
In another aspect, the present invention provides an apparatus for correcting the curve radius of the lane on which the vehicle is traveling, comprising: a means of detecting the curve radius by a curve detection sensor; a means of determining whether a curve radius is wrong based on the first detected position and the present position of a leading vehicle; a means of computing a virtual curve radius based on the detected information about the leading vehicle; and a means of synthesizing the horizontal relative position for the curve radius and the horizontal relative position for the virtual curve radius.
In the present invention, the curve radius obtained by the ACC system of a vehicle is corrected only when the straight lane on which the vehicle is traveling is considered to be a curve lane by mistake. The movement in the horizontal direction of an approaching vehicle in front of the vehicle is monitored, and when the approaching vehicle has moved out of the expected range, the curve radius is corrected. The correction is performed by assigning weights to the horizontal relative position computed based on the curve radius obtained by the ACC-EUC, and to the horizontal relative position computed based on the virtual curve radius obtained from the position of the approaching vehicle detected by the radar.